High Lockout
70 on Alpha E-Tec Regular

Your boiler has detected a problem with the sensor that monitors water temperature as it returns from your heating system, causing the unit to stop running for safety.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Return flow sensor error

What causes this fault?

This fault occurs when the boiler's internal computer receives an incorrect or missing signal from the sensor that monitors water coming back from your radiators. The most common reason is that the sensor itself has developed an electrical fault or the wiring connecting it to the main control board has become loose or damaged.

Engineer required

This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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